1. Field of the Invention
The present invention relates to a system for protecting the health of the visually handicapped such as those afflicted with blindness or near blindness and, particularly, to a system which compensates for the relative inability of blind people to provide maximum personal safety when moving on or about the platform of a public railway transit system while approaching a train with the intention of boarding one of its coaches. Although no completely reliable statistics are available, the most widely used estimates in 1994 place the legally blind population of the United States at 2.24 per thousand (that is, approximately 500,000) Approximately 50,000 become legally blind annually, and many others have enough visual loss to pose a serious employment problem (General Ophthalmology, Vaughn et al, Norwalk, Conn., Appleton & Lange, 1992).
2. Description of the Related Art
The expansion of high speed railway transit systems to many major cities throughout the world, while viewed by many as merely another sign of technological achievement associated with a modern society, is generally undertaken with less than adequate consideration of the problems of persons who are physically handicapped. It is unfortunate that this sweeping hypothesis finds greater application when applied to the blind. The requirements imposed on designers of public railway transit systems by the Americans with Disabilities Act is a step in the direction of recognizing the needs of a minority population using modern technology to enhance the safety and accessibility of subway systems for the blind or visually impaired. One such effort is being prepared in response to a request by the Washington Metropolitan Area Transit Authority (WMATA) for assistance to comply with requirements recently laid down by the Federal Transit Authority. The federal requirements, in turn, are intended to promote development which will improve the accessibility to users who have little or no forward vision. One particular desire underpinning these requirements is to design ways to identify platform edges and other potential safety hazards to a class of commuters who lack the sense of sight needed to detect and avoid such hazards. Although the particular requirements of the Federal Transit Authority are quite specific as to the set of users targeted to benefit, design requirements can be considered to resemble a general type of synthetic environment system in which a personal user interface system is used to translate a sensory environmental signal of one type into sensory user inputs of a different type. When placed into practice, this concept may be implemented by replacing visual clues not ordinarily available to the blind or visually impaired with substitute inputs such as the auditory or tactile kind.
The Federal Transit Authority originally mandated the installation of strips of truncated domes or bumps mounted on the platform floor near the edge, in two-feet widths, to act as an underfoot tactile warning to the blind as they walk into this region. Promoters of this design operated under the premise that when such bumps are detected underfoot the subway user will recognize impending danger and come to a halt before reaching the edge of the platform. WMATA, with the support of the National Federation of the Blind, objected to the Maginot Line concept for several reasons, including the following:
1. The bump strips are not effective enough: visually impaired travellers are first made aware of the platform edge by the bumps at a distance which is short when one considers the range of human reaction times--most people must slow down and anticipate the edge long before the final two feet.
2. The bump strips are potential safety hazards to sighted as well as visually impaired people as something to trip over, for example, those wearing high heels, operators of wheelchairs, strollers and the like. At the very least, they call attention by a non-aesthetic marring of the subway platform to attempt to accommodate a very small number of commuters.
3. Bump strips are unnecessary for many skilled blind or visually impaired users who have been trained to navigate efficiently with sound cues and by cane without interfering with habits of sighted passengers.
4. The bump strips do not address more serious difficulties in subway stations, such as the ability to discriminate between the door openings in rail cars and the openings between rail cars, location of escalators, elevators, fare card machines, etc.
5. Any solution proposing platform bumps is expensive based on WMATA estimates to install and maintain such a system.
6. The use of truncated-dome system is not voluntary.
7. There is no distance-from-the-platform edge information which can be extracted from this implementation.
The NFB has recommended that technology can be applied to develop an equivalent facilitation warning system that is less costly, has the additional benefit of being voluntary (for users), provides additional information, and is extendible to other access and area identification problems. The warning signal should be virtually undetectable to sighted users and should not require blind or visually impaired users, who wish to take advantage of the technology, to do anything extraordinary to use it. Moreover, in using the system one should appear natural and should not require extensive or complex training. It should be easy to use, even by people who have little or no familiarity with technical devices.
Intruder indication is provided for in U.S. Pat. No. 5,126,718 but the system described therein depends upon the reflection of infrared radiation from an intruder entering a protected field of view. The system described in U.S. Pat. No. 4,712,003 provides a blind person guide device whose sonar can indicate bearing and distance from an object in which the distance to an object lying in the direction in which the range finder faces is transmitted or perceived as vibrations felt through the handle of a walking stick. Neither of the prior art apparatus addresses a particular danger faced by blind people who out of necessity rely on rail transportation.